A revised relaxation-time spectrum for Fennoscandia

• Published in: Geophysical Journal International
• Main Authors: Wieczerkowski, Karin, Mitrovica, Jerry X., Wolf, Detlef
• Format: Text
• Language: English
• Published: Oxford University Press 1999
• Subjects: Articles; Fennoscandia; Fennoscandian
• Online Access: http://gji.oxfordjournals.org/cgi/content/short/139/1/69; https://doi.org/10.1046/j.1365-246X.1999.00924.x

The Fennoscandian relaxation-time spectrum (RTS), first derived by <cross-ref type="bib" refid="bib13">McConnell (1968</cross-ref>), is a classic data set in studies of glacial isostatic adjustment (GIA). We outline a new method for estimating an RTS from a set of strandline data, which is based on a damped least-squares solution for spherical harmonic coefficients associated with the strandline heights. In contrast to the Hankel transform approach outlined by <cross-ref type="bib" refid="bib13">McConnell (1968</cross-ref>), the method does not require interpolation or extrapolation of the data, nor does it use the assumption that peripheral deformations are zero. We begin by applying the new approach to a suite of synthetic strandlines. These synthetic calculations quantify the effect on the RTS estimates of the common assumptions of free-decay uplift, an axisymmetric Fennoscandian deformation field, and the uncertainty introduced by limited spatial and temporal sampling of this field. Recently, the accuracy of the <cross-ref type="bib" refid="bib26">Sauramo (1958</cross-ref>) strandline data upon which the <cross-ref type="bib" refid="bib13">McConnell (1968</cross-ref>) RTS was based has been questioned (<cross-ref type="bib" refid="bib33">Wolf 1996</cross-ref>); accordingly, we apply our new approach to a set of more robust strandline data published by <cross-ref type="bib" refid="bib4">Donner (1964</cross-ref>, <cross-ref type="bib" refid="bib5">1969, 1980, 1995</cross-ref>) to compute a revised RTS for Fennoscandia. At high harmonic degrees (above 50), our new RTS is characterized by weak constraints, whereas <cross-ref type="bib" refid="bib13">McConnell's (1968</cross-ref>) RTS suggests a significant reduction in relaxation times relative to the values at low degrees. This reduction was the basis for <cross-ref type="bib" refid="bib13">McConnell's (1968</cross-ref>) inference of an elastic ...